This is not too much trouble if you use a Lvl.75 character on Hero difficulty. I used a Warrior class char. but this guide could be used with the others too.
I found the best tactic was to:
1. Play the pit of Trials with my Lvl.75 char. until I picked up a decent Red bow.
2. Re-spec my character points and pile them all into dexterity and strength 50/50 (maybe all dex. would work too) and pile all skill points into the skills that increase damage.
3. The key when fighting the Fairy Queen is to keep your distance and fire arrows into her. At first her attacks are a bit unpredictable and she will sporadically launch purple fireball things at you, but if you keep your distance you should have enough time to see them coming and avoid them.
4. Once she is suitably aggro-ed, her attacks become very predictable. She will try and strike you with lightning but you'll be able to see when this is about to happen by the white patch that appears under your character. Simply run round her clockwise (or anti), take a few shots at her, then when the white appears underneath you, run round a couple of hours (positionally speaking
), take a few more shots (I found that I could safely take a couple of shots before running on again, 3 was a bit riskier) then the white mark will appear again, move around the clock another couple of hours and pop off some more shots.
5. Rinse and repeat